(a) Field of the Invention
The present invention relates to an automatic transmission for vehicles More particularly, the present invention relates to a damper clutch control method for an automatic transmission which can improve drive performance when the vehicle runs on a slope.
(b) Description of the Related Art
In a vehicle using an automatic transmission, engine power is transmitted to an input shaft of the transmission through a torque converter. To improve the power transmission efficiency, the torque converter is designed having a damper clutch disposed between a turbine and an impeller. That is, when the damper clutch is operated or engaged, the engine is directly connected to the input shaft of the transmission.
The operation of the damper clutch is controlled in accordance with an engine rpm, a throttle opening and a vehicle speed. That is, a transmission control unit TCU analyzes a rotational slip rate between the impeller and the turbine according to the engine rpm, the throttle opening and the vehicle speed, then directly connects the damper clutch with the input shaft according to the analyzed results to improve the fuel-consumption ratio and maintain vehicle speed.
However, in the conventional art, since the control of the damper clutch operation is set only on the basis of a flat road, it is difficult to improve the driving performance when the vehicle runs on a slope. That is, the conventional damper clutch is designed not to operate in a low-speed range (up to the vicinity of 60 km/h), deteriorating the fuel consumption ratio.
Therefore, the present invention has been made in an effort to solve the above problems.
It is an objective of the present invention to provide a damper clutch control system for an automatic transmission which can improve a driving performance of a vehicle when the vehicle runs on a slope.
To achieve the above objective, the present invention provides a damper clutch control method of a hydraulic control system for automatic transmissions, the hydraulic control system comprising a drive condition detecting part for detecting a drive condition of a vehicle and outputting corresponding signals, a pressure control solenoid valve, a transmission control unit for duty-controlling the pressure control solenoid valve in accordance with the signals from the drive condition detecting part, and a damper clutch control valve for selectively supplying hydraulic pressure to a damper clutch in accordance with the operation of the pressure control solenoid valve, the damper clutch control method comprising the steps of calculating a damper clutch operation condition according to signals from the drive condition detecting part, determining if the calculated value is within a damper clutch operation range on a level road, controlling, when the calculated value is within the damper clutch operation range, the pressure control solenoid valve such that the damper clutch can be operated by hydraulic fluid fed through the damper clutch control valve, determining if a damper clutch release condition on a level road is satisfied or not, controlling, when the damper clutch release condition is satisfied, the pressure control solenoid valve such that the damper clutch can be released by releasing hydraulic fluid from the damper clutch.
The damper clutch control method may further comprise the steps of determining if the damper clutch operation on a slope is satisfied or not when the damper clutch operation condition on the level road is not in the damper clutch operation range, calculating the gradient of the slope when the damper clutch operation on the slope is satisfied, determining if a slope running time is longer than a standard running time when the calculated gradient is greater than the standard gradient, duty-controlling, when the slope running time is longer than the standard running time, the pressure control solenoid valve such that the damper clutch control valve supplies hydraulic pressure to the damper clutch to operate the damper clutch, calculating a gradient of the slope, determining if a damper clutch release condition under the calculated gradient is satisfied or not, and controlling, when the damper clutch release condition under the calculated gradient is satisfied, the pressure control solenoid valve such that the hydraulic pressure fed to the damper clutch is released.
The standard gradient is about 5%.
The standard running time is about 5 seconds.